jstates simple example

jstates_simple_example.js

const createState = require("jstates");

const myState = createState({ counter: 0 });

function onUpdate(state) {
  console.log("onUpdate: counter =", state.counter);
}

myState.subscribe(onUpdate);
myState.setState(state => ({ counter: ++state.counter }));
// => onUpdate: counter = 1